BIOLOGIST STEPHEN Jay Gould died of cancer last month at the age of 60.

Gould was one of the most influential evolutionary theorists of his generation, the world’s leading expert on the evolution of Caribbean land snails, and the most talented popularizer of science in the past century. His monthly column, This View of Life, ran for 300 consecutive issues in Natural History magazine from 1974 to 2001. It used examples, ranging from church architecture to baseball (Gould’s other passion), to explain the complexities of biology.

Gould’s ability to convey complex scientific ideas without oversimplifying them, his immense learning and his polished literary style won him a huge readership. Ten collections of his essays – the last, I Have Landed, published just weeks before his death – became bestsellers.

By the 1990s, Gould was a household name. In 1997, he made an animated guest appearance on The Simpsons, and last year, the Library of Congress named him one of America’s “living legends.”

NO WONDER every major newspaper carried an obituary of Gould last month. But few said much about his radical politics.

Gould’s parents were New York leftists, and he once boasted that he had “learned his Marxism, literally at his daddy’s knee.” More recently, Gould added that his politics were “very different” from his father’s, perhaps indicating his own rejection of Stalinism.

Whatever he meant, Gould remained politically active his whole life. While a visiting undergraduate in England in the early 1960s, Gould organized demonstrations outside a segregated dance hall until it admitted Blacks. Back in the U.S., he was an early opponent of the Vietnam War.

When Harvard students shut down their campus in 1969 to protest the university’s involvement in the war, Gould – by then an assistant professor – supported them. “Lacking tenure, or a bankable reputation,” recalls writer Michael Ryan, a Harvard undergraduate at the time, “he sided with [antiwar] students when junior faculty brown-nosers were looking the other way.”

Gould was often seen on picket lines and at demonstrations. When residents of a racially mixed, working-class Cambridge neighborhood rebelled against police brutality in 1971, Gould joined a Students for a Democratic Society march to support the uprising. At around the same time, Gould joined Science for the People, one of the radical science organizations that emerged from the antiwar movement.

Later, Gould was on the advisory boards of the journal Rethinking Marxism and the Brecht Forum, sponsor of the New York Marxist School, which is dedicated to using “Marx’s uniquely valuable contributions to study conditions today and possibilities for transcending capitalism and building an emancipatory society.”

The Encyclopedia of the American Left singled Gould out as one of the “few scientists [who] have emerged as major public allies of the Left” and as “perhaps the most formidable example of a supportive presence at Left events and for Left causes.”

GOULD’S SCIENTIFIC work showed the influence of his political background.

In 1975, to great media fanfare, Gould’s prominent Harvard colleague Edward Wilson published his book Sociobiology, which argued that traits such as aggression and xenophobia are genetically based.

Gould and other members of Science for the People responded by rejecting Wilson’s ideas as the latest version of a scientifically bankrupt biological determinism. “The reason for the survival of these recurrent determinist theories,” they wrote in a letter to the New York Review of Books, “is that they consistently tend to provide a genetic justification for the status quo and of existing privileges for certain groups according to class, race or sex.”

In opposition to determinism, Gould emphasized the enormous flexibility of human behavior. “Violence, sexism, and general nastiness are biological since they represent one subset of a possible range of behaviors,” he wrote. “But peacefulness, equality, and kindness are just as biological – and we may see their influence increase if we can create social structures that permit them to flourish.”

Gould continued this critique in his award-winning 1981 book, The Mismeasure of Man, one of the best arguments against scientific racism and the idea that intelligence is genetically fixed.

In the 1990s, when Bell Curve authors Charles Murray and Richard Herrnstein tried to revive these racist ideas and provide pseudo-scientific support for slashing social spending and ending affirmative action, Gould took them on. Gould provided new material that showed how Herrnstein and Murray omitted facts and misused statistical methods to reach their racist conclusions.

In exposing the social roots of scientific ideas, Gould followed in the footsteps of one of his intellectual heroes, Frederick Engels – Karl Marx’s close collaborator. Gould praised Engels’ 1876 pamphlet The Part Played by Labor in the Transition from Ape to Man. In it, Engels correctly rejected the claim that “our evolution was propelled by an enlarging brain” and offered a “perceptive analysis of the political role of science and of the social biases that must affect all thought.”

But in placing science in its social context, Gould was also careful to reject the claim of relativists who abandon the idea of objective truth altogether. “I share the credo of my colleagues,” he wrote. “I believe that a factual reality exists and that science, though often in an obtuse and erratic manner, can learn about it.”

Gould also shared Engels’ enthusiasm for understanding the natural world dialectically – in other words, consisting of complex and dynamic interactive processes. “Dialectical thinking should be taken more seriously by Western scholars, not discarded because some nations of the second world [the former Soviet Bloc] have constructed a cardboard version as an official political doctrine,” Gould wrote.

“When presented as guidelines for a philosophy of change, not as dogmatic precepts true by fiat, the classical laws of dialectics [formulated by Engels] embody a holistic vision that views change as interaction among components of complete systems, and sees the components themselves as both products and inputs to the system.”

WITH FELLOW paleontologist Niles Eldredge, Gould proposed the theory of “punctuated equilibrium.” The two argued that evolutionary development isn’t gradual, as Charles Darwin supposed, but takes place in concentrated bursts, followed by long periods of stasis.

Gould freely admitted that he was attracted to the theory because of his knowledge of Hegel and Marx. But while his political background made him open to an idea he might otherwise have ignored, Gould emphasized that he accepted the theory because of the evidence.

Punctuationism was only one of Gould’s contributions to evolutionary thought. Against reductionists like Richard Dawkins, who argue that everything important takes place at the level of the gene, Gould argued that natural selection can operate on groups, species and lineages, as well as on genes and individual organisms.

Gould and his colleague Richard Lewontin rejected the “ultra-Darwinian” idea that natural selection is the only important evolutionary mechanism. Many features of organisms, they argued, are the result of structural constraints, rather than adaptive advantage. In The Structure of Evolutionary Theory, a 1,500-page tome published in March, Gould defended this evolutionary pluralism at length.

Critics sometimes claimed that the debates Gould provoked gave comfort to religious opponents of evolution. But Gould was also the most prominent public critic of “creation science.” He pointed out that evolution is a fact – and that “[f]acts do no go away while scientists debate rival theories for explaining them.”

It was certainly possible to take issue with some of Gould’s views. While rightly arguing that evolution is not a linear process with humans as its inevitable outcome, Gould sometimes seemed to deny that there are any evolutionary trends. And in a recent book, he argued unconvincingly that there is no fundamental conflict between science and religion.

But Gould’s contributions to evolutionary biology will live on. And his commitment to the view that science can be a tool for liberation, not oppression, should inspire everyone who wants not just to understand the world, but to change it for the better.